There is a considerable body of prior art in the design of fan-type snowmaking apparatus wherein a high velocity stream of subfreezing ambient air is forced through a tubular housing from an open inlet to a coaxial outlet where water is sprayed into the air stream. This mixture of water and air propelled from the outlet end of the tubular housing is especially effective in making artificial snow if a nucleating device is provided in the tubular housing upstream of the water injection at the outlet end. A nucleating device sprays a mixture of fine droplets of water and pressurized air into the main air stream flowing through the tubular housing by air displacement means such as a motor-driven fan. The minute droplets of water generated by the nucleator attract moisture to form larger crystals more closely comparable to natural snow.
The most common conventional location for a nucleator nozzle is on the central axis of the tubular housing downstream of the fan, as exemplified by the designs in U.S. Pat. Nos. 3,733,029, 3,945,567 and 4,813,598. The fan or other air displacement means in such a configuration typically includes a drive motor coaxial with the fan axis, usually with some form of cowling over the motor, and a nucleator disposed coaxially downstream of that apparatus is necessarily in its lee so that the nucleator is not directly in the highest velocity air stream flow where its seeding of ice crystal nuclei can be most effective.
In U.S. Pat. No. 5,167,367 a design is disclosed wherein a multiple-orifice nucleator is located at a six o'clock position upstream of the water injection means instead of on the axis of the tubular housing, but even in that design the nucleator orifices are on the leeward side of a reservoir component tilted at an angle facing downstream, and hence are not directly in the air stream flow. A circular array of nucleator nozzles concentric with and spaced radially from the tubular housing axis is shown in U.S. Pat. No. 5,180,106 but they are completely shielded from the air stream flow by a fixed central cylindrical shroud.
To locate nucleator nozzles radially away from the axis of the tubular housing directly in the subfreezing air stream flow, and not in the protective lee of the coaxial fan and motor or some shroud such as that required in U.S. Pat. No. 5,180,516, can create serious icing problems. When compressed air mixes with water in the nucleator nozzle a subfreezing air stream impinging directly upon the nucleator may very well cause the water component in the nucleator to form rime ice which can clog the nucleator nozzle.
It is a principal purpose of the present invention to provide a nucleator assembly which will be located at a region of maximum effectiveness directly within the cold air stream flow through the tubular housing, and not in the lee of any upstream fan motor or shroud, and which enhances the mixing of air and water in the nucleator while preventing freezing of the water as it mixes with the air. Motionless mixers are well known for enhancing the mixing of certain viscous fluids, as taught for example in U.S. Pat. Nos. 4,840,903 and 4,850,705, but those devices generally are applicable to the mixing of viscous fluids in plastic injection molding processes or epoxy and resin static mixers. Motionless mixers of that form have not previously been utilized for water and air mixing in nucleators for snowmaking equipment.